This invention relates generally to a guiding or positioning apparatus for use during hitching a pickup truck or other towing vehicle to a trailer or other towed vehicle. More particularly, this invention relates to a positioning apparatus for aligning the coupling elements of the two vehicles as the towing vehicle is backed up or driven toward the towed vehicle and for indicating when the coupling elements are positioned to be coupled.
Hitching a vehicle to a trailer can be a long and frustrating process, especially when attempted by a single person. Because the coupling elements (i.e., ball and hitch) on the vehicle and trailer are normally not visible from the driver's seat, the driver must periodically stop the vehicle and inspect the alignment and position of the ball and hitch before moving the vehicle closer to the trailer. Even with frequent visual inspections, some misalignment of the ball and hitch normally result. A driver must then repeat the process or, if possible, manually shift the tongue and thus the hitch of the trailer over the ball so that the two vehicles can be hooked up. Complicating the maneuvering is the fact that a driver can become easily confused as to which direction to turn the front wheels in order to back the vehicle in the desired direction.
In an attempt to improve on this manual method, prior guidance systems have been designed for assisting a driver in maneuvering a vehicle toward a trailer. U.S. Pat. No. 3,924,257 to Roberts, for example, discloses a trailer hitch guide that uses a transmitting coil on a trailer and orthogonally arranged receiving coils on the back of a vehicle. The transmitting coil produces a hemispherical magnetic field that can be detected by the receiving coils on the vehicle. This patent recites that, depending on the orientation of the receiving coils to the field, the alignment and position of the vehicle relative to the trailer can be determined from a direction indicator visible to the driver. The Roberts device, however, is understood to have a number of drawbacks. For example, magnetic field decreases in strength dramatically with distance, limiting the effective range of a device such as Roberts. Also, it is believed that the Roberts device may not always accurately indicate the relative position of the hitch and ball due to limitations of the Roberts approach.
Other exemplary prior devices for guiding the backing of a vehicle to a trailer are disclosed in U.S. Pat. No. 4,199,756 to Dito, U.S. Pat. No. 2,984,011 to Hamilton, and U.S. Pat. No. 3,418,628 to Fenner. These devices rely on mechanical contact switches or visual alignment mechanisms that are cumbersome and/or which must be mounted temporarily to a vehicle and trailer for use when attempting to back up and hitch the two together.